Intravascular devices with high tungsten content

ABSTRACT

Implantable medical devices, such as embolic devices and blood flow filters are disclosed, the devices being made at least partially out of a platinum-tungsten alloy, wherein a percentage of tungsten in the alloy is equal to or greater than about 10% of the alloy by weight.

FIELD

The presently disclosed inventions relate generally to medical devices.More particularly, the present disclosure relates to medical devices,such as intravascular implants, composed of a combination of platinumand tungsten metal alloy.

BACKGROUND

The use of intravascular medical devices has become an effective methodfor treating many types of vascular disease. Intravascular medicaldevices such as stents, filters, thromboembolic capture devices, flowdiverters, vaso-occlusive devices, collectively referred to herein as“medical devices” are often composed of a variety of biocompatiblematerials, including polymers (e.g., non-biodegradable and biodegradableplastics) and/or metals. Some of these medical devices are formed by oneor more elongate members (e.g., wires, drawn-filled tubes, threads,filaments and the like) that are woven into a braid or mesh pattern.Such braided devices may be utilized for treating various types ofvascular defects, such as aneurysms, and may be provided in a widevariety of respective delivery and deployed sizes and shapes;particularly, secondary shapes when the device is deployed in a targetedvasculature site. Some exemplary secondary shapes of braided devicesinclude spherical, ovoid, flat ribbon, helical braided ribbon, orcombinations thereof, suitable for the treatment of vascular defects. Ingeneral, a suitable intravascular implantable device is inserted intothe vascular system of the patient and navigated through the vasculatureto a targeted implantation site using known delivery systems andmethods.

Medical devices can be made from shape memory or superelastic materials,such as shape memory metals (e.g., shape memory Nitinol) and polymers(e.g., polyurethane). Such shape memory embolic devices can be induced(e.g., by temperature, electrical or magnetic field or light) to take ona shape (e.g., a radially expanded shape) after delivery to a treatmentsite. Superelastic materials, such as superelastic Nitinol, take on ashape after delivery without the need for an inductive stimulus. Drugdelivery medical devices can carry, and/or the surface of the device,can be coated with a bioactive or therapeutic agent (e.g., thrombosisinducing agent).

Various physical attributes of the medical devices can contributedirectly to the success rate of the device. These physical attributesinclude radiopacity, hoop strength, radial force, column strength,flexibility and dimensions of the material used to form the device andthe like. Cobalt-chromium (Co—Cr) and stainless steel are commonly usedto form stents. These materials are commonly used since such materialshaving a known history of safety, effectiveness and biocompatibility.These materials however have limited physical performancecharacteristics as to size, strength, weight, bendability, biostabilityand radiopacity.

Other commonly used materials include platinum, platinum and tungstenmetal alloy, and elgiloy. Known medical devices composed ofplatinum-tungsten alloy (Pt—W) are illustrated and described (by way ofexample) in U.S. Pat. Nos. 6,322,576, 6,458,119, 7,842,054, 9,198,670and 9,597,155, and U.S. Publication No. 20070162108. However, thesedisclosures are either silent with respect to the specific percentage ofplatinum and tungsten in the metal alloy or they expressly disclose apreferred or desirable combination of the alloy having platinum (92%)and tungsten (8%) (i.e., Pt-8% wtW).

Due to higher modulus and mechanical strength, some more recentimplantable devices including blood flow diversion stents are being madeout of Cobalt-chromium (Co—Cr) alloys designed to have suitable radialforce. However, the Co—Cr devices have undesirable properties, such assubstantially higher magnetic susceptibility of Magnetic ResonanceImaging (MRI) resulting in MR image artifact and poor radiopacity. Forthe known platinum/tungsten (Pt—W) alloys, up to 8% tungsten (W) hasbeen alloyed to the platinum (Pt) to enhance mechanical strength,handling, and manufacturability. Alloying tungsten (W) greater than 8%is not generally considered because additional tungsten (W) in theplatinum (Pt) matrix generally increases its brittleness, compromisingthe performance of the Pt—W alloy. Although commonly used Pt-8% wtWalloy has relatively low magnetic susceptibility of MRI and higherradiopacity than Co—Cr, the Pt-8% wtW alloy has been found to be notsuitable for such flow diversion stents due to the low modulus of thealloy, which results in an undesirably low radial expansion force. Inparticular, the 8% tungsten (W) was added to the platinum (Pt) alloy toenhance mechanical strength, handling and manufacturability. However,adding more than 8% tungsten (W) has not been explored due to expectedincreased brittleness of the Pt—W alloy.

SUMMARY

Embodiments of the disclosed inventions are directed to implantablemedical devices, such as embolic devices and blood flow filters, thatare at least partially made out of (i.e., composed of) aplatinum-tungsten alloy in which a percentage of tungsten in the alloyis equal to or greater than about 10% by weight, and preferably in arange of between about 10% to about 20% by weight.

In various embodiments, the implantable devices are made out of one ormore elongate members composed of the platinum-tungsten alloy, such asin the form of a cut tube, a coiled wire, or a plurality of wires wovenin a braided configuration. Without limitation, the elongate members mayinclude composite wires having at least one layer made out of theplatinum-tungsten alloy.

Although it has been traditionally believed in the art of makingimplantable medical devices that a platinum-tungsten alloy having apercentage of tungsten over 8% is not manufacturable, throughexperiment, the present inventors discovered that a platinum-tungstenalloy having a percentage of tungsten that is at least 10% by weightcould not only be manufactured but would unexpectantly have severaladvantageous properties. By way of example, and without limitation, suchunexpected advantageous properties include having a substantiallygreater ultimate tensile strength, a substantially greater Young'smodulus, and a substantially reduced magnetic susceptibility,respectively, than substantially identically dimensioned alternativematerials composed of a platinum-tungsten alloy having a percentage oftungsten that is about 8% by weight.

Other and further aspects and features of embodiments of the hereindisclosed inventions will become apparent from the ensuing detaileddescription in view of the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1C are perspective, detailed and cross-sectional views of abraided stent/flow diverter constructed according to embodiments of thedisclosed inventions;

FIGS. 2A-2B are cross-sectional and perspective and view of an emboliccoil constructed according to embodiments of the disclosed inventions;and

FIGS. 3A-3F are perspective views of an intravascular device constructedaccording to embodiments of the disclosed inventions.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

For the following defined terms, these definitions shall be applied,unless a different definition is given in the claims or elsewhere inthis specification.

All numeric values are herein assumed to be modified by the term“about,” whether or not explicitly indicated. The term “about” generallyrefers to a range of numbers that one of skill in the art would considerequivalent to the recited value (i.e., having the same function orresult). In many instances, the terms “about” may include numbers thatare rounded to the nearest significant figure.

The recitation of numerical ranges by endpoints includes all numberswithin that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4,and 5).

As used in this specification and the appended claims, the singularforms “a”, “an”, and “the” include plural referents unless the contentclearly dictates otherwise. As used in this specification and theappended claims, the term “or” is generally employed in its senseincluding “and/or” unless the content clearly dictates otherwise.

Various embodiments of the disclosed inventions are describedhereinafter with reference to the figures. The figures are notnecessarily drawn to scale, the relative scale of select elements mayhave been exaggerated for clarity, and elements of similar structures orfunctions are represented by like reference numerals throughout thefigures. It should also be understood that the figures are only intendedto facilitate the description of the embodiments, and are not intendedas an exhaustive description of the disclosed inventions, or as alimitation on the scope thereof, which is defined only by the appendedclaims and their equivalents.

In addition, the respective illustrated embodiments of the disclosedinventions need not have all of the depicted features, and a feature,aspect or advantage described in conjunction with a particularembodiment is not necessarily limited to that embodiment, but can bepracticed in other embodiments, even if not so illustrated.

Metal Alloy

In various embodiments of the disclosed inventions, a metal alloycomprising platinum and tungsten (Pt—W) having a percentage (i.e.,hereafter mass or weight percentage) of tungsten (W) that is equal orlarger than 10% of the alloy, is used in the manufacturing of medicaldevices. In some embodiments, the percentage of tungsten (W) ranges from10% to 20% of the alloy. In those embodiments the remaining percentageof the alloy is composed mostly of platinum (Pt), such as for example,where the percentage of platinum (Pt) is equal or less than 90% of thealloy when the percentage of tungsten (W) that is equal or larger than10%, or where the percentage of platinum (Pt) is equal or less than 80%of the alloy when the percentage of tungsten (W) that is equal or largerthan 20%.

In the embodiments of disclosed inventions, the percentage of tungsten(W) is equal or larger than 10% of the platinum/tungsten (Pt—W) alloyused to form the medical devices. Having the percentage of tungsten (W)as equal or larger than 10% of the platinum/tungsten (Pt—W) alloyforming the medical devices provides for improved properties compared toknown medical devices having 8% or less of tungsten (W) in theplatinum/tungsten (Pt—W) alloy.

As noted above, although conventional wisdom has been that it is notadvisable to increase the percentage of tungsten in a platinum-tungstenalloy used for constructing implantable medical devices, the presentinventors, when considering and studying the Pt—W phase diagram,believed that Pt-high W content alloys may nonetheless be of some value.From theoretical analysis, the inventors expected there might be someimprovements in mechanical strength of the resulting alloy. However,experimentation using Pt-16% W alloy demonstrated exceptionally good andunexpected results with respect to improved mechanical properties,increase in radiopacity (which is critical for blood flow diverterdevices) and, most surprisingly, a substantial reduction in magneticsusceptibility (little or no change had been expected).

These unexpected properties of the disclosed platinum/tungsten (Pt—W)alloy comprises, one or more of the following exemplary properties, suchas: column strength, radial strength, hoop strength, tensile strength,tensile elongation, stress-strain properties, radial force, radiopacity,flexibility, bendability, heat sensitivity, biocompatibility, and thelike. Particularly, a medical device composed of a percentage oftungsten (W) that is equal or larger than 10% of the platinum/tungsten(Pt—W) alloy may increase: radiopacity, radial strength, hardness, yieldstrength and/or ultimate tensile strength of the device; and/or mayfurther improve stress-strain properties of the device, crimping and/orexpansion properties, bendability and/or flexibility, overall strengthand/or durability of the device, longitudinal lengthening properties,recoil properties, friction coefficient, heat sensitivity properties,biostability and/or biocompatibility properties, and/or enablemanufacturing of smaller, thinner and/or lighter weight medical devices.For example, a medical device composed of a percentage of tungsten (W)that is equal or larger than 10% of the platinum/tungsten (Pt—W) alloy,is configured to have a Young's modulus of equal or larger than 30 Ksi.Additionally, or alternatively, medical devices composed of a percentageof tungsten (W) that is equal or larger than 10% of theplatinum/tungsten (Pt—W) alloy are configured to have a magneticsusceptibility in the range of 10 ppm to 300 ppm resulting in reducedartifact during MR imaging.

For example, current flow diversion stents composed of cobalt-chromium(Co—Cr) alloys have substantially higher magnetic susceptibility of MRI(i.e., MR artifact) and poor radiopacity. Thus, making MR follow upimaging not suitable for implanted flow diversion stents made of Co—Cr.In some instances, to improve radiopacity of flow diversion stents madeof Co—Cr, Pt-8% W alloy wires are blended with CoCr wires. However, flowdiversion stents composed of a percentage of tungsten (W) that is equalor larger than 10% of the platinum/tungsten (Pt—W) alloy, allows for asuitable superior radiopacity and radial force due to the high modulus,as compared for example the CoCr alloy. Additionally, flow diversionstents composed of a percentage of tungsten (W) that is equal or largerthan 10% of the platinum/tungsten (Pt—W) alloy have substantially lowmagnetic susceptibility for MR artifact, allowing MR follow up imagingfor implanted flow diversion stents.

These one or more improved properties of the medical device composed ofa percentage of tungsten (W) that is equal or larger than 10% of theplatinum/tungsten (Pt—W) alloy may be achieved without having toincrease the volume and/or weight of the device. Further, these improvedproperties are likely to be obtained when the volume and/or weight ofthe medical device is reduced as compared to devices that are at leastpartially formed from known materials, such as stainless steel,cobalt-chromium (Co—Cr), or platinum/tungsten (Pt—W) alloy having equalor less than 8% of tungsten (W).

Moreover, as long as the percentage of tungsten (W) is equal or largerthan 10% of the platinum/tungsten (Pt—W) alloy, it should be appreciatedthat the percentage of platinum (Pt) in the alloy may be less than the90% to 80% range, such that other materials may be present. In thoseembodiments, the platinum/tungsten (Pt—W) alloy may comprise smallerpercentage (e.g., 5% or less) of other elements. For example, titanium(Ti) in order to obtain a reduced level of radiopacity, or zirconium(Zr), hafnium (Hf), and/or gold (Au) to achieve desirable levels ofmagnetic susceptibility, or tantalum (Ta), iridium (Ir), rhenium (Re),rhodium (Rh), ruthenium (Ru) and/or molybdenum (Mo) to obtain desirablelevels of mechanical properties, including any combination thereof ofthese elements or any other suitable element.

Further, medical devices composed with the disclosed platinum/tungsten(Pt—W) alloy having a percentage of tungsten (W) that is equal or largerthan 10% of the alloy, may include one or more materials that impartdesired properties to the device so as to withstand the manufacturingprocesses that are needed to produce the device. These manufacturingprocesses include, for example, laser cutting, etching, crimping,annealing, drawing, pilgering, electroplating, electro-polishing,chemical polishing, cleaning, pickling, ion beam deposition orimplantation, sputter coating, vacuum deposition, or the like.

By way of non-limiting examples, the disclosed platinum/tungsten (Pt—W)alloy is at least 95% of the medical devices. Further, the disclosedplatinum/tungsten (Pt—W) alloy having a percentage of tungsten (W) thatis equal or larger than 10% may be used to form devices such as forexample: stents (e.g., slotted tube stents and/or braided or wovenstents), filters, thromboembolic capture devices, flow diverters,vaso-occlusive devices, intrasaccular aneurysm implants, vasculardelivery assemblies, catheters, reinforcement members, guidewires,delivery wires, radiopaque markers and the like.

By way of non-limiting examples, the disclosed platinum/tungsten (Pt—W)alloy having a percentage of tungsten (W) that is equal or larger than10% of the alloy configured to at least partially forms the medicaldevice. For example, the alloy may form the majority weight percent ofthe medical device but that may not be required.

By way of example, the embodiment of FIG. 1A-3F depict medical devicesconstructed with the disclosed platinum/tungsten (Pt—W) alloy having apercentage of tungsten (W) that is equal or larger than 10% of thealloy.

FIGS. 1A-1C illustrate an exemplary braided embolic device in the formof a tubular braided stent and/or flow diverter 10, constructedaccording to the one embodiment of the disclosed inventions. FIG. 1Ashows the braided stent 10 in a radially expanded deliveredconfiguration, having a proximal portion 12, a distal portion 14 and alumen 16 extending therebetween. The braided stent 10 is formed out of aplurality of elongate members 20 (e.g., wires, drawn-filled tubes,threads, filaments and the like) that are woven together. FIG. 1B is atwo-dimensional plan view of a section of a wall 18 of the braided stent10, showing that the elongate braid members 20 are woven in a standardrepeating “one-over, one-under” pattern 50 (detailed of FIG. 1A), whichis a common weave pattern used in known braided embolic devices. One ormore of the elongated members 20 are composed of the disclosedplatinum/tungsten (Pt—W) alloy having a percentage of tungsten (W) thatis equal or larger than 10%. The elongated members 20 of FIGS. 1A-1B caninclude a ribbon-like configuration having substantially rectangularcross-section (FIG. 1C). As further shown in FIG. 1C, the ribbon-likeelongated members 20 comprise a width (W1) of 0.004″ (0.102 mm) and aheight (H1) of 0.002″ (0.051 mm). In some embodiments, the ribbon-likeelongated members 20 comprises a maximum width of 0.005″ (0.127 mm) anda minimum height of 0.0008″ (0.0203 mm). In further embodiments wherethe elongated members 20 have substantially circular cross-section(not-shown), the diameter of the circular cross-section of the elongatedmembers 20 are in the range between 0.0008″ (0.0203 mm) to 0.004″ (0.102mm), and preferably, in the range between 0.001″ (0.025 mm) to 0.002″(0.051 mm). It should be appreciated that the elongated members 20 mayinclude other cross-sectional configurations.

In the embodiments of FIGS. 1A-1B, the braid pattern 50 or specificationof the braid of the stent 10 includes between 36 to 144 elongatedmembers 20; preferably between 48 to 120 elongated members 20.Additionally, the radially expanded delivered configuration of thebraided stent 10 have a PPI between 30 to 200; preferably between 50 to150.

Referring back to the disclosed platinum/tungsten (Pt—W) alloy having apercentage of tungsten (W) that is equal or larger than 10% forming oneor more of the elongated members 20, provides the stent 10 with thefollowing properties: a) the stent 10 would achieve higher radial forcedue to higher material modulus and strength; b) the stent 10 isconfigured to be manufactured of smaller elongated members 20 and with agreater wire count to achieve better flow diversion effect; c) the stent10 is configured to have a reduced MR image artifact for follow upimaging procedures due to low magnetic susceptibility, making the stent10 more suitable for MR imaging and/or the stent 10 is configured tohave full radiopacity, and other advantages, previously disclosed.Further, if the radiopacity of the stent 10 is too high for theapplication, the device can be manufactured using a combination ofelongated members 20 composed of the disclosed platinum/tungsten (Pt—W)alloy and another material or alloy with lower radiopacity, or thedevice can be manufactured using a composite wire that consists of thedisclosed platinum/tungsten (Pt—W) alloy as an external layer andanother less radiopaque alloy as the core. The above disclosedproperties of the stent 10 composed of the disclosed platinum/tungsten(Pt—W) alloy having a percentage of tungsten (W) that is equal or largerthan 10% forming one or more of the elongated members 20, are incomparison with stents composed of cobalt-chromium (Co—Cr) alloys orwith stents made out of other available materials.

FIGS. 2A-2B illustrate an exemplary intrasaccular device in the form ofan embolic coil 100, constructed according to the embodiments of thedisclosed inventions. The coil 100 is formed of a helically wound wire102 having a first end 104 and a second end 106. The coil 100 includes astretch-resisting member 108 that is fixedly attached both to the firstend 104 and to the second end 106. In alternative embodiments, thestretch-resisting member 108 may be attached to one of the two ends orto neither of the two ends. The coil 100 of FIG. 2A is shown in a“primary” winding or shape, and the coil 100 of FIG. 2B is shown in a“secondary” winding or shape. The secondary shape of the coil 100 ofFIG. 2B forms a substantially spherical three-dimensional shape havingnon-overlapping loops 120. It should be appreciated that secondary shapeof the coil 100 may assume any other suitable shape. The wire 102 ofcoil 100 may be formed of a single wire, drawn-filled tubes, threads,filaments or the like. In some embodiments, the wire 102 diameter (D1)ranges from about 0.0005″ (0.0127 mm) to about 0.005″ (0.127 mm), theprimary wind diameter (D2) of the coil 100 ranges from about 0.003″(0.0762 mm) to about 0.030″ (0.762 mm) and/or the secondary winddiameter (D3) ranges from about 0.5 mm to about 50 mm, as shown in FIGS.2A-2B.

The wire 102 of coil 100 (FIGS. 2A-2B) is composed of the disclosedplatinum/tungsten (Pt—W) alloy having a percentage of tungsten (W) thatis equal or larger than 10%. Where the coil 100 is composed with thedisclosed platinum/tungsten (Pt—W) alloy—as, for example compared tocoils composed of platinum with 8% tungsten (Pt-8W)—the coil 100includes the following properties: a) due to the higher modulusresulting in higher column strength the coil 100 is configured tosupport a longer length without corresponding larger wire 102; b) due tohigher yield strength, the coil 100 is configured to be a more effectiveframing device; c) due to the stability of the alloy, the coil isconfigured to achieve better shape retention, and deliverability forcoils to treat small aneurysms (e.g., under 2 mm due to combination ofhigher strength and higher modulus).

As previously disclosed, the coil device composed of the disclosedplatinum/tungsten (Pt—W) alloy having a percentage of tungsten (W) thatis equal or larger than 10% of the wire, has lower MR artifact due tolow magnetic susceptibility as compared to the current coils composed ofPt-8% W alloy.

FIGS. 3A-3F illustrate an exemplary braided intravascular device havingan atraumatic end member, constructed according to the embodiments ofthe disclosed inventions. FIG. 3A shows the braided intravascular device200 in a radially expanded (i.e., unconstrained) configuration, having aproximal portion 220, a distal portion 240, and a lumen 260 extendingtherebetween. The braided intravascular device 200 is formed out of aplurality of elongate members 250 (e.g., wires, drawn-filled tubes,threads, filaments and the like) that are woven (or “braided”) together.The braided intravascular device 200 includes an atraumatic member 270(e.g., coil or the like) at the distal portion 240 of the device 200, asshown in FIG. 3A. It should be appreciated that another atraumaticmember 240 may be disposed at the proximal portion 220 of the device 200(shown in FIG. 3B). The individual elongate members 250 may havesubstantially circular cross-sections (FIG. 3C), with a cross-sectionaldiameter in a range of between about 0.0005″ (0.0127 mm) to about 0.003″(0.0762 mm). The diameter (D4) of the intravascular device 200 may be inthe range of between about 0.01″ (0.25 mm) to about 0.2″ (5 mm). Itshould be appreciated that the individual elongate members 250 may haveother suitable cross-sections, such as for example, rectangular withrounded corners (FIG. 3D), rectangular with square corners (FIG. 3E),ovoid (FIG. 3F) or the like. The device 200 may also have different,i.e., non-tubular, cross-sectional shapes in their expandedconfigurations, such as a flattened rectangle with rounded corners (notshown).

One or more of the elongated members 250 and/or the atraumatic member270 are composed of the disclosed platinum/tungsten (Pt—W) alloy havinga percentage of tungsten (W) that is equal or larger than 10% where oneor more of the elongated members 250 and/or the atraumatic member 270are composed with the disclosed platinum/tungsten (Pt—W) alloy, theyinclude the following properties: a) due to the higher modulus resultingin higher column strength the intravascular device 200 includes a bettertransition between the elongated members 250 and/or the atraumaticmember 270; b) the intravascular device 200 may comprise a smallerprofile for delivery through smaller internal diameter catheters into atarget site of a patient.

Experimental Data

In accordance with the disclosed inventions, experiments were conductedon devices composed of disclosed platinum/tungsten (Pt—W) alloy having apercentage of tungsten (W) that is equal or larger than 10% of thedevice or portions thereof. A sample wire made of the disclosedplatinum/tungsten (Pt—W) alloy (Pt-16% W) and having a diameter of0.0011″ (0.02794 mm) was tested to confirm properties of the disclosedalloy and compared to the commonly used Pt-8% W with same wire diameterof 0.0011″. Both wires having an elongation of approximately 2%. Thesample wire composed of the disclosed platinum/tungsten (Pt—W) alloy(Pt-16% W) and having a density of 21.08 g/cm3 comprises an ultimatetensile strength (UTS) of 470 Ksi, a Young's modulus of 36 Msi andmagnetic susceptibility of 23 ppm. In comparison, the commonly usedPt-8% W wire having a density of 21.26 g/cm3 has an ultimate tensilestrength (UTS) of 200-250 Ksi, a Young's modulus of 26 Msi and magneticsusceptibility of 69 ppm.

Therefore, the wire composed of a platinum/tungsten alloy that isapproximately 16% tungsten by weight showed approximately a 100%improvement in mechanical strength, approximately a 40% increase inYoung's modulus, and approximately a 65% reduction in magneticsusceptibility, respectively, over a substantially identicallydimensioned wire composed of a platinum-tungsten alloy that isapproximately 8% tungsten by weight. Notably, the disclosed inventionsinclude—without limitation—the various above-described embodiments ofimplantable medical devices formed out of wires or filaments having thesame attributes as the tested wire made from the platinum/tungsten alloythat is approximately 16% tungsten by weight.

Although particular embodiments have been shown and described herein, itwill be understood by those skilled in the art that they are notintended to limit the disclosed inventions, and it will be obvious tothose skilled in the art that various changes, permutations, andmodifications may be made (e.g., the dimensions of various parts,combinations of parts) without departing from the scope of the disclosedinventions, which is to be defined only by the following claims andtheir equivalents. The specification and drawings are, accordingly, tobe regarded in an illustrative rather than restrictive sense. Thevarious embodiments shown and described herein are intended to coveralternatives, modifications, and equivalents of the disclosedinventions, which may be included within the scope of the appendedclaims.

What is claimed is:
 1. An implantable medical device, comprising: one ormore elongate members composed of a platinum-tungsten alloy, wherein thepercentage of tungsten in the platinum-tungsten alloy is equal to orgreater than about 16% by weight.
 2. The device of claim 1, wherein theone or more elongate members comprise a cut tube.
 3. The device of claim1, wherein the one or more elongate members comprise a plurality ofcomposite wires, each having at least one layer composed of theplatinum-tungsten alloy.
 4. The device of claim 1, wherein the one ormore elongate members comprise a plurality of wires or filaments wovenin a braided configuration.
 5. The device of claim 1, wherein thepercentage of tungsten in the platinum-tungsten alloy is a range fromabout 16% to about 20% by weight.
 6. The device of claim 5, wherein thepercentage of tungsten in the platinum- tungsten alloy is about 16% byweight.
 7. The device of claim 6, wherein the one or more elongatemembers comprise a wire having an ultimate tensile strength that isapproximately 100% greater than an ultimate tensile strength of asubstantially identically dimensioned alternative wire composed of analternative platinum-tungsten alloy having a percentage of tungsten thatis about 8% by weight.
 8. The device of claim 6, wherein the one or moreelongate members comprise a wire having a Young's modulus that isapproximately 40% greater than a Young's modulus of a substantiallyidentically dimensioned alternative wire composed of an alternativeplatinum- tungsten alloy having a percentage of tungsten that is about8% by weight.
 9. The device of claim 6, wherein the one or more elongatemembers comprise a wire having a magnetic susceptibility that isapproximately 60% less than a magnetic susceptibility of a substantiallyidentically dimensioned alternative wire composed of an alternativeplatinum-tungsten alloy having a percentage of tungsten that is about 8%by weight.
 10. An implantable medical device, comprising: a plurality ofwires woven in a braided configuration, wherein at least a subset ofwires of the plurality are composed of a platinum-tungsten alloy havinga percentage of tungsten in a range from about 16% to about 20% byweight.
 11. The device of claim 10, wherein the wires of the subsetcomprise composite wires, each including at least one layer composed ofthe platinum-tungsten alloy.
 12. The device of claim 10, wherein atleast some wires of the subset composed of the platinum-tungsten alloyhave non-circular cross-sections.
 13. The device of claim 12, whereinthe non-circular cross-sections are selected from the group comprising:rectangular with rounded corners, rectangular with square corners, andovoid.
 14. The device of claim 10, wherein the subset of wires composedof the platinum-tungsten alloy have a greater ultimate tensile strength,a greater Young's modulus, and a lesser magnetic susceptibility,respectively, than substantially identically dimensioned alternativewires composed of an alternative platinum-tungsten alloy having apercentage of tungsten that is about 8% by weight.
 15. An implantableocclusive device, comprising: a wire composed of a platinum-tungstenalloy, wherein the percentage of tungsten in the platinum-tungsten alloyis equal to or greater than about 16% by weight, and wherein the wire iswound into an elongate helical coil.
 16. The device of claim 15, whereinthe helical coil is treated to assume a three-dimensional secondaryshape when unconstrained.
 17. The device of claim 16, wherein thesecondary shape is substantially spherical.
 18. The device of claim 16,wherein in the secondary shape, the coil has non-overlapping loops. 19.The device of claim 15, wherein the wire is a drawn-filled tube.
 20. Thedevice of claim 15, wherein the wire has a diameter in a range fromabout 0.0005″ (0.0127 mm) to about 0.005″ (0.127 mm), and wherein thecoil has a primary wind diameter in a range from about 0.003″ (0.0762mm) to about 0.030″ (0.762 mm).
 21. The device of claim 15, wherein thewire has a greater ultimate tensile strength, a greater Young's modulus,and a lesser magnetic susceptibility, respectively, than substantiallyidentically dimensioned alternative wire wound into a coil and composedof an alternative platinum-tungsten alloy having a percentage oftungsten that is about 8% by weight.